1. Field of the Invention
The present invention relates to a power steering apparatus for assisting steering operation by generating steering assist force by driving force of motor during steering operation of car or the like.
2. Related Background Art
An example of such power steering apparatus of an electric motor type is shown in FIG. 13 (Japanese Laid-open Patent Application No. Sho 62-214055). Pinion shaft 101 in mesh with rack 102 is connected through torsion bar 104 to steering shaft 103 and the tip of steering shaft 103 is connected to a steering wheel not illustrated. In the periphery around the torsion bar 104, spur gear 105 is provided so as to rotate together with these pinion shaft 101, torsion bar 104, and steering shaft 103, and this spur gear 105 is connected in mesh through intermediate gear 106 with gear 107, thus composing a reducing unit. Then this gear 107 is connected through clutch 108 to an output shaft of electric motor 109. This structure forms a mechanism for transmitting the driving power of electric motor 109 through the clutch 108, gear 107, and intermediate gear 106 to the spur gear 105, thereby supplying the steering assist force during the steering operation.